1. Field of Invention
This invention relates to the field of fogging mechanisms, particularly insecticide fogging type mechanisms. A full definition of proper insecticide fogging, as it relates to this invention is the dispensing of an insecticide in controlled micro-particulate form in metered quantities into a known-volume area, such as, for example, processing or storage areas of a food processing plant. In a situation such as a food processing plant, it is necessary to periodically and regularly dispense insecticide into the atmosphere of the food processing plant as an environmental control measure to maintain a clean and insect free environment. The most effective, safe and economical such fogging systems or mechanisms currently available employ compressed air or the like as the propellant. The insecticide is disbursed into the atmosphere in micro-particulate form by forcing a mixture of liquid insecticide and pressurized air or the like through one or more nozzles, which nozzles are specially designed fogging nozzles. By forcing liquid insecticide and pressurized air or the like through such nozzles, the liquid insecticide is broken down into micron size particles capable of remaining suspended in the atmosphere. In that way, insecticide in micro-particulate form, or in other words, an insecticide fog, is dispensed into the atmosphere.
For the purpose of this invention, "fogging" is defined as the process of dispensing a liquid, such as insecticide, into the atmosphere in particle size sufficiently small to provide that the particles remain suspended in the atmosphere for a discernible period of time. In this definition, fogging is distinguished from "spraying" in that spraying contemplates the dispensing of particles of a size large enough so that individual particles fall rapidly onto some surface and do not remain suspended. Fog from a spraying operation is an undesirable byproduct. A typical example of a fogging system is the West Chemical Products, Inc., insecticide dispensing system.
The effectiveness of an insecticide fogging system and the insecticide fog dispensed thereby depends upon many inter-related and variable factors, beginning with the insecticide itself. When fogged, the individual particles of insecticide must be of sufficient concentration to kill the insect species involved and must at the same time be small enough and uniform enough to remain suspended in the atmosphere for a sufficient period of time to fully cover the volume of air space involved. Therefore, the insecticide utilized must first be properly formulated to retain its killing power when broken down into micro-particulate form of particle size small enough to remain suspended in the atmosphere. Once the proper insecticide is determined and utilized, the other variable factors then become dominant. These factors are the quantity of insecticide fog dispensed and the particle size. They are direct functions of pressure, volume and time as these factors relate to supplied propellant. In the final determination of insecticidal fog effectiveness, these other factors are of equal importance to the insecticide itself. They are not adequately controlled with present portable fogging systems; it is the function of this design mechanism to provide such control.
Propellant pressure is normally provided from an external source. With the total cross-section or orifice and piping sizes of a given fogging system being a constant, the volume of propellant, such as compressed air passing through that system, is a function of pressure. At a given nozzle adjustment as long as the externally supplied pressure remains constant, the amount of insecticide dispensed as fog becomes constant per unit of time. Also, under these conditions, particle size of the insecticide fog remains constant.
The amount of insecticide needed for a given application will normally be indicated in the label instructions for that particular insecticide in terms of ounces of insecticide required as fog per thousand cubic feet of air space. Thus, when a known, constant quantity of insecticide fog per unit of time of effective particle size can be delivered, the amount of insecticide needed for a given volume of air space becomes a direct mathematical function of operating time.
2. Prior Art
Little has been done in this area to develop effective means of controlling the period of time during which an insecticide fogging system is allowed to operate or the pressure under which the system operates. Generally, the time period has been left to direct operator control and the pressure has been left to the normal variances of the available external sources, which provides less than adequate control over the amount of insecticide dispensed or the particle size of the insecticide dispensed.
Generally speaking, the insecticide fogging systems utilized are portable systems. This is so because of the fact that the volume of the air space of any food processing plant or the like is generally larger than can be effectively fogged by stationary or permanently mounted fogging nozzles. For this reason, among others, electrical time control has proved ineffective because of lack of coordination between the positioning of electrical power outlets and pressurized air outlets within a food processing plant or the like. This same situation exists when any attempt is made to adapt any other type of time control necessitating an additional external source of power to operate a time control device other than pressurized air outlets within the environment of a food processing plant or the like. Consequently, portable fogging systems have remained essentially devoid of any means of time and pressure control or for that matter any means of control of other variables which are directly related to the effective control of the amount and quality of insecticide fog being dispensed.
Elaborate permanent, stationary, in-house fogging systems have been proposed to include stationary, strategically positioned nozzles combined with a plant wide delivery system and control system. However, systems of this nature have generally proved ineffective, extremely expensive, and difficult to maintain. Any system of this nature, of necessity, becomes extremely elaborate. This is partially due to the fact that the volume of air space involved in most food processing plants or the like is so large that it is usually impossible to provide adequate amounts of pressurized air to operate the entire system and all nozzles thereof simultaneously. Consequently, it then becomes necessary to provide a central control system which will sequentially activate groups of nozzles, zone by zone, within different zones of the food processing plant or the like in question. This need for sequential operation complicates the control system to the extent that the system becomes unjustifiably expensive and cumbersome.